Dietary L-arginine supplementation differentially regulates expression of lipid-metabolic genes in porcine adipose tissue and skeletal muscle.
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Obesity is a major health crisis worldwide and new treatments are needed to fight this epidemic. Using the swine model, we recently reported that dietary L-arginine (Arg) supplementation promotes muscle gain and reduces body-fat accretion. The present study tested the hypothesis that Arg regulates expression of key genes involved in lipid metabolism in skeletal muscle and white adipose tissue. Sixteen 110-day-old barrows were fed for 60 days a corn- and soybean-meal-based diet supplemented with 1.0% Arg or 2.05% L-alanine (isonitrogenous control). Blood samples, longissimus dorsi muscle and overlying subcutaneous adipose tissue were obtained from 170-day-old pigs for biochemical studies. Serum concentrations of leptin, alanine and glutamine were lower, but those for Arg and proline were higher in Arg-supplemented pigs than in control pigs. The percentage of oleic acid was higher but that of stearic acid and linoleic acid was lower in muscle of Arg-supplemented pigs, compared with control pigs. Dietary Arg supplementation increased mRNA levels for fatty acid synthase in muscle, while decreasing those for lipoprotein lipase, glucose transporter-4, and acetyl-coenzyme A carboxylase- in adipose tissue. Additionally, mRNA levels for hormone sensitive lipase were higher in adipose tissue of Arg-supplemented pigs compared with control pigs. These results indicate that Arg differentially regulates expression of fat-metabolic genes in skeletal muscle and white adipose tissue, therefore favoring lipogenesis in muscle but lipolysis in adipose tissue. Our novel findings provide a biochemical basis for explaining the beneficial effect of Arg in improving the metabolic profile in mammals (including obese humans).